Abstract: Alternating current impedance and corrosion resistance of polymer coatings on sheet iron have been investigated in aqueous solution of NaCl with mass ratio of 0. 03.The time dependence of the resistance was calculated by experimental value of the capacitance.Thoretical and experimental results are coincident very well.Experiments showed that the capacitance is an important parameter of evaluating corrosion resistance. The results showed that polymer coatings prepared by using solidifying agent of higher solidity and activity thinner are helpful to increasing corrosion resistance.the dR/dt increases with the thickness of coating.